Polycarbonate Copolymer Coloration Control

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Solution Overview

Problem

Polycarbonate copolymers used in electrophotographic photoreceptors face issues with coloration, which affects transparency and electrostatic characteristics, and existing methods for reducing impurities are either complex or not easily applicable, leading to increased residual potential after repeated use.

Innovation Solution

A polycarbonate copolymer is developed through polycondensation using a biphenol monomer with a trihydroxy biphenyl content of 300 mass ppm or less, ensuring minimal coloration and improved electrostatic characteristics, suitable for optical materials and electrophotographic photoreceptors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If a biphenol skeleton is included in the polycarbonate copolymer, then heat resistance is improved, but coloration occurs and transparency deteriorates

Engineering Contradiction:

Improveheat resistanceVSAvoidcoloration

Core Design Contradiction:

TemperatureVSObject-affected harmful factors

Solution Approach 1:

The patent changes the chemical composition parameters by strictly controlling the trihydroxy biphenyl content to 300 mass ppm or less, while maintaining the biphenol skeleton structure. This parameter control allows the polymer to retain heat resistance while minimizing coloration through precise compositional adjustment.

Inventive Principle:

Principle #35Parameter changes

2Temperature

If a biphenol skeleton is included in the polycarbonate copolymer, then heat resistance is improved, but electrostatic characteristics worsen and residual potential increases

Engineering Contradiction:

Improveheat resistanceVSAvoidelectrostatic characteristics

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The patent adjusts the compositional parameters by limiting trihydroxy biphenyl content to 300 mass ppm or less, which optimizes the balance between heat resistance and electrostatic characteristics. This parameter control prevents excessive residual potential while maintaining thermal stability.

Inventive Principle:

Principle #35Parameter changes

3Object-affected harmful factors

If existing methods are used to reduce impurities, then coloration is reduced, but manufacturing complexity increases

Engineering Contradiction:

ImprovecolorationVSAvoidmanufacturing complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by controlling the trihydroxy biphenyl content at the monomer stage before polymerization. This preventive approach ensures low impurity levels in the final product without requiring complex post-polymerization purification processes.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent simplifies manufacturing by establishing a clear parameter threshold (300 mass ppm or less for trihydroxy biphenyl content) that can be monitored and controlled during monomer preparation, avoiding the need for complex multi-step purification procedures.

Inventive Principle:

Principle #35Parameter changes

4Object-affected harmful factors

If existing methods are used to reduce impurities, then coloration is reduced, but the methods are not easily applicable and increase manufacturing difficulty

Engineering Contradiction:

ImprovecolorationVSAvoidease of manufacture

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The patent makes impurity reduction easily applicable by implementing control measures at the monomer preparation stage. This preliminary action allows standard manufacturing processes to produce low-coloration polymers without requiring specialized equipment or complex operational procedures.

Inventive Principle:

Principle #10Preliminary action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The copolymer exhibits reduced yellowish index (YI) values, maintaining transparency and stability, and effectively prevents the increase in residual potential of electrophotographic photoreceptors after repeated use, making it suitable for both optical and electronic applications.

Implementation Method 1

a polycarbonate copolymer formed through polycondensation of a monomer represented by the formula (3) and a monomer represented by the formula (4)

Methodology Applied

Scientific EffectPolycondensation:

Data Source

PatentEP2570447B1Polycarbonate copolymer, method for producing the same, molded body, optical material, and electrophotographic photosensitive body

Publication Date: 2016.04.06 IDEMITSU KOSAN CO LTD

AI summary

A polycarbonate copolymer is formed through polycondensation of a monomer represented by a formula (3) as follows and a monomer represented by a formula (4) as follows. The content of a biphenyl compound having three phenolic hydroxyl groups in one molecule in the monomer represented by the formula (3) is 300 mass ppm or less. In the formula R1 and R2 each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. In the formula R3 and R4 each independently represent a hydrogen atom, an aliphatic hydrocarbon group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms or a halogen atom; and X represents any one of bonding groups represented by -O-, -S-, -SO-, -SO2-, -CO- and 9,9- fluorenylidene group.